"The severity of an earthquake can be expressed in terms of both intensity and magnitude. The two terms are quite different, however, and they are often confused. Intensity is based on the observed effects of ground shaking on people, buildings, and natural features. It varies from place to place within the disturbed region depending on the location of the observer with respect to the earthquake epicenter. Magnitude is related to the amount of seismic energy released at the hypocenter of the earthquake. It is based on the amplitude of the earthquake waves recorded on instruments, which have a common calibration. Magnitude is thus represented by a single, instrumentally determined value."

"The Richter magnitude scale was developed in 1935 by Charles F. Richter of the California Institute of Technology as a mathematical device to compare the size of earthquakes."

"The deadliest quake of all time might be one of the least talked about, considering it occurred nearly 450 years ago. Centered in China's central Shaanxi province, the 1556 quake claimed the lives of some 830,000 people." 03-10

"It's been known for a long time that humans could induce earthquakes by pumping fluids underground. Back in 1962, the U.S Army injected toxic waste fluids into a deep well at the Rocky Mountain Arsenal northwest of Denver, but then stopped after the area was rattled over five years by more than 1,500 quakes, including one that shook chandeliers at the state Capitol and forced legislators to take cover."

"Seismologists' big concern is not the fracking process itself, but what what operators do with the enormous quantities of waste water that flows back out of the well afterward. "

"One company has developed a system that uses gelled propane instead of water. Because the fluid merges into the oil and gas being extracted, it could eliminate the need to drain away waste water. Friction-reducing additives also eventually could allow operators to keep reusing the same water in wells, instead of having to dispose of it." 03-15

"Through this lesson, the student will come to understand the significance of the 1906 San Francisco earthquake through the study of primary documents. The student will also apply his/her research skills to the study of primary documents from various other key historical events." 04-06